


Don't Drink Mysterious Pink Liquids

by MapleMeSyrup



Category: Undertale (Video Game)
Genre: Alternate Universe - Underswap, Boob Growth, Dom!Blueberry, F/M, Lactation Kink, NSFW, Please forgive me for my sins, Underswap Sans, Underswap Sans X Reade, i just have a huge lactation kink
Language: English
Status: Completed
Published: 2017-04-05
Updated: 2017-04-05
Packaged: 2018-10-15 02:08:16
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 1,502
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/10548240
Author URL: https://archiveofourown.org/users/MapleMeSyrup/pseuds/MapleMeSyrup
Summary: You drink a potion and call Blueberry for help. The two of you have wild night.





	

**Author's Note:**

> I got a request for Dom Sans and a lactation kink and I just HAD to make a one shot of it.  
> Like my stuff? Follow my Undertale headcanon blog [Skelltales](http://www.skelltales.tumblr.com)

You rummage through the kitchen just for something, anything, to quench your unsustainable thirst. Hell, you’d even go for some of Papyrus’s honey right now. You spy a bright pink liquid in a transparent sports bottle, hidden behind some leftover tacos. As if the gods had illuminated a ray of sunshine on it, you grab the bottle and chug the entire content in one go, the sweet, flower flavor fizzing on your tongue and bringing rain to the desert. Tossing the bottle into the sink, you sigh in relief, your thirst thoroughly vanquished. You grab a book from the bookshelf and stretch over the couch, deciding that this is going to be most productive thing you’ll do today. Your boyfriend, Sans or sometimes Blue, and his brother Papyrus had already left for work that morning, leaving you some time to relax and enjoy the silence on your day off. As you position yourself comfortably on the couch, you flip through the pages of your book, unaware about the changes about to happen. 

As you read through your novel, your body becomes increasingly hot and your skin drips in a sticky clear sheen of light sweat. Annoyed by your discomfort, you walk across the room to turn on the fan, the sudden cool blast hardening your nipples as it strains against your black tank top. You shiver from the small shock of pleasure, but ignore it and return to your reading. You don’t notice that with each passing minute, your breasts begin to thrust and expand, flying by cup by cup. Finally, your chest tightens and your breathing becomes restricted to the point where you have to put your book down to figure out what the heck is going on. You gasp loudly and drop the book on the floor. 

“What the fuck!” you exclaim as you grasp your still growing chest, “What’s going on?!” 

You lift up your heavy mounds, both pushing past what you figure to be double Ds. The sensitivity increases, growing stronger and stronger as your boobs approach the size of basketballs. Finally, it comes to a full stop and you take off your tank top, curiously running your hands around your boobs, exploring every inch of your new breasts. You always wanted bigger boobs, but come on! This is ridiculous! You can’t go out in public looking like a fucking sex doll! And oh god, why do they feel so full? 

“This can’t be happening…”

Suddenly, your fingers against your erect nipples and your knees shake just from the pure dripping pleasure. Normally, playing with your nubs wouldn’t feel good as this, but oh god, it’s like rubbing two clits, doubling and increasing the tingling shocks. You can’t stop yourself as you continue to rub and rub, then like a dam breaking through, you scream in ecstasy as your mind goes blank just from playing with your tits, your fluids flying everywhere. Collapsing on your hands and knees, you moan as your body shudders, riding out the last bit of the orgasm. Your mind goes fuzzy as you catch your breath, syncing to the rhythm of your rapid heartbeat. Something warm drips on your stomach and you look down to see a slow, steady stream of glistening white milk flowing from your nipples. You scream and cover your chest as if that will somehow stop the flow. Suddenly, your phone rings and you reach for it with trembling hands. 

“H-Hello?” you answer?

“(Y/N)! H-Hi!” you recognize Undyne’s voice through the speaker, “Is uh, Papyrus home?” 

“No, he went to work with Blue,” you reply, your breath shaking as the milk flows in between your fingertips. 

“Oh,” the monster sighs in disappointment, “Well, when you see him, could you tell him to bring me the pink juice? He took a sample home and I need it back for further testing,”

“T-The pink juice?” your blood runs cold. 

“Yeah! It’s a potion that Papy and I are developing together to help nursing mothers with their milk production,” on her end, something loud crashes, “Oh no! I gotta go now. Tell Papyrus to bring me the juice!”

“Undyne wait!”

Click. 

Lowering your head in your hands, you wish that this is all a dream. A dream that you will wake up from, probably wet and horny, and one that you’ll use for many future sessions…

Fuck! You pull your hands away from your damp crotch and grab a towel to soak up the milk. Having no idea what to do, you’re scared, alone, and horny as fuck so you call the one person you trust the most. 

“Good morning (Y/N)! You’re up early!” Sans picks up on the third ring. 

“S-Sans? Could you come home please? It’s an emergency,” you huff as you feel your boobs becoming heavier. 

“What’s wrong? Did something happen?” concern flows through his voice. 

“Just...come home. I need you,” you cry. 

“I’ll be right there!” before you could hang up a blue light flashes in the living room, “(Y/N)! Are you okay? Wha….uhhhhh….WHAT HAPPENED TO YOUR BOOBS?!” 

“AH! SANS!” you instantly cover your chest, you face completely flustered and embarrassed, “I drank some of Papyrus’s potion and it...made me this way.” 

“Okay, why don’t I call Papy to figure out what to do?” Sans says, his eyes trained on your bouncing bust, “You might want to, uh, clean up.” 

Deciding that a cold shower is exactly what you need, you grab a towel and lock the bathroom door, allowing the cool spray to wash away the milk residue and the weirdness of today’s events. Thankfully the leaking stopped for now, but you could still feel the sloshing from inside you and your excruciating arousal burns in between your legs. Since none of your shirts will fit you now, you scurry to your room and throw on a fresh pair of underwear and grab a silk kimono robe that Undyne got you for your birthday. Your everlasting hard nipples dents the fine fabric, pleasuring you every time you move. Blue knocks on the door and you let him inside. 

“I just called Papy and he said that the effects should only last a day. After that, everything would be back to normal, including your size,” Sans explains, basically drooling at your cleavage. 

“That’s a relief,” you sigh. 

“Also,” Sans’s eye flares blue and he flashes in front of you, throwing you on the bed and pinning your hands above your head, “My brother won’t be home until tomorrow.” 

The skeleton cups your breasts through your robes, loosening them until they’re free, his breath hitching at your round orbs. He fondles them gently, barely letting his bones touch your soft skin, all while avoiding your hyper sensitive nipples, which are thick with need.Your face flushes red and your sex is already dripping wet and ready for him. 

“Mwhehwh, you’ve been busy without me, haven’t you?” Blue’s eyes darkens as his breath tingles your skin, “Now, how should I play with you?” 

“Please, Sans, I need you,” you groan, rubbing your clit over your panties. 

“Really? Is that all you want from the Magnificent Sans?” your boyfriend lightly strokes your inner thigh. 

“No, I - Ah,” Sans licks his teeth and in that moment, you stop fighting everything and just give in, “Please play with my body! Pinch my nipples! Play with my tits! Pound me til I can’t walk! I don’t care! Just fuck me!” 

“Mwhehehe you asked for it!” Sans dives into your boobs, taking a long nipples into his mouth, and sucks. 

Grasping the bedsheets under you, you spasm against his hold as your milk flows freely into his mouth and he continues to suckle until you’re dry, moving onto the next as he discards your underwear and rub your clit in tight circles. 

“Look at you,” Sans huffs as he pulls out his cyan hard dick and rubs it against your hole, “So wet and pretty for me. You like this don’t you? You like having big boobs filled with milk. So tasty, so delicious,”

“Y-Yes!” you moan as he pinches your nipples, a spurt of milk spraying on his face which he licks away with his tongue, “I love it! I love being your cow!” 

Oh god, you did not just say that. But Blue’s eyes lights up like twinkling stars and he rams his dick inside of you, pounding you roughly and using your oversize boobs as a grip, squeezing them so hard that milk flies everywhere. You scream his name over and over as he brings you to an orgasm three times, each one lasting longer than the others til all you can think of is his name. Finally, you feel his dick throb and he pulls out of you, moaning your name as he cums all over your tits. Panting hard, Sans collapses on top of you, nuzzling your chest and using them as pillows. 

“We should ask Papyrus to make more,” Blue purrs. 

“Agreed.” 

**Author's Note:**

> Any kind of feedback will be appreciated ^_^


End file.
